Pressure control system



Jan. 19, 1943. D. GREGG ETAL. Y ,3 0 4 PRESURE CONTROL SYSTEM Filed Jan. 4, l94l mvsmons. I Dav/d Gregg 'Dona/d M. Lawrence Patented Jan..19, 1943 David Gregg, creates, and Donald N. 3., assignors to Bendix Aviation Newark,

M- Lawrence,

Corporation, South Bend, Ind, a corporation oi Delaware Y Application January 4, 1941, Serial No. 873,178

2 Claims. res-204) This invention relates to pressure systems and more particularly to the design of a multi-stage supercharger for aircraft cabins.

High altitude flying in scheduled transportation and in military missions has been advanced because of the sealin and supercharging of the cabins containing passengers and crew. Several systems for the accomplishment of the necessary supercharging have been designed, but none of these systems, prior to the present invention, have taught how to avoid the excessive heatin of the inlet air at low altitudes, or have the flexibility necessary to maintain cabin pressures under difierent flight conditions which may be met with in varying altitudes with compression and. volum demands varying within wide limits.

It is an object of the present invention to provide a multi-stage supercharging system for aircraft cabins, wherein the cooling of hot inlet air may be accomplished by the circuit arrangement of the supercharging system.

It is another object of the invention to provide a flexible supercharging system which, depending upon the pressure demand in a cabin, may automatically be changed from a single to multiple stage operation.

Further objects include the provision of a system adapted for single or multi-stage operation by a simple adjustment, and of a means, in a multi-stage system, for cooling or heating the air at will.

Other objects will appear from a study of the following specification when made in conjunction with the attached drawing, throughout which like numerals designate like parts. I

Fig. 1 is aschematic diagram of one embodiment of the present invention; and

' Fig. 2 is a schematic diagram of a second embodiment of the present invention,

In accordance with the present invention, two superchargers, one of which has a capacity greater than the other, have individual air input conduits, and have their output capable of connection to an aircraft cabin either in series or in parallel, depending upon the pressure and volume requirements to be met. Several automatic check valves, and one or more motor or manually controlled valves, are supplied in the air connections between the two superchargers and between the cabin, for permitting single or multistage operation, and also for accomplishing the cooling or heating of input air before its entrance to the cabin, under particular operating conditions.

Having particular reference to Fig. 1, super- 15. An additional conduit sand feet regardless of charger no, of the Roots type, as shown, has an air inlet or scoop H, which may be located in a leading portion of the aircraft, and an output or exhaust conduit 52 in which there is placed a valve is capable of manual or motor operation through the valve arm and rod it. One outlet of valve I3 connects to a conduit IS on the input side of a second supercharger it. The capacity of supercharger to is greater than the capacity of supercharger it. The difierencein capacity may be on the order of 25 to and may be obtained in any of'several ways: for example, the superchargers may be. of equal physical dimensions but driven (by the same or by separate englues) at different speeds, or they may be of different physical dimensions and driven at the same speed (by the same or by different engines).

Input conduit i5 is open to an air intake or scoop H, which may be placed in the leading portion of the aircraft, having a check valve is which permits the entrance of air through scoop ll under certain pressure conditions, but prevents exlt of air therethrough. The output of supercharger it is connected by a. conduit It to the input of cabin 28. Another check valve 2!, which permits flow of air into conduit I9 and cabin 2B, is placed in a conduit 22, which is in communication with output air flowing from supercharger l0 through conduit l5 and with input air flowing into supercharger it through conduit 23' is providedbetween output conduit I2 and conduit l9 and acts as a by-pass for air from supercharger to under certain conditions of operation.

When valve I3 is in its open position, as shown, the sup r arging system is. in condition for twostage operation, the condition of operation that gives themaximum pressure range of the system, so that cabin pressure may be maintained at any desired value from sea levelto ten thouexternal pressures atthe higher altitudes. At the lower altitudes, because of the high external pressures, air compressed in supercharger It drives supercharger it as a motor, due to its inferior capacity, returning work to the engine driving supercharger i6 and expanding the air in the output IQ of supercharger I6, thus decreasing its temperaturer A part of the air in conduit 15, due to its compression in supercharger I0 and to the low capacity of supercharger l6, enters cabin 2% through valve 2| and conduit 22 As the altitude of the craft increases, the input pressure to supercharger l0 decreases, and thus the pres= sure in conduit 15 decreases, so that a greater amount of air is accepted throu h supercharger l6 and less flows through valve 2|. Finally, as external pressure continues to drop, the back pressure of cabin 20 becomes equal to the pressure in conduit l5, and valve 2| closes, making supercharger the first stage of a two-stage system,

and supercharger l6 compresses air from conduit [5. which enters conduit I 9 and cabin 20 at a pressure greater than that of theatmosphere and greater than that in conduit Hi. It is understood that the correct pressure for cabin 20 may be maintained by means of any suitable pressure control system, forexample, that described in the co-pendlng case of David. Gregg, Serial No. 372,692, filed December 31, 1940.

If, particularly at the lower altitudes, there is an unusual demand for-a larger volume of air, then superchargers may be thrown into parallel operation by the closure of conduit l5 by valve H3, in its vertical position. Air compressed in supercharger l then goes directly to cabin 20 through conduit 23, and valve l8 opens to admit air through scoop II, which is compressed in supercharger i6 and fed to cabin 20 through conduit l9. Since the pressure in conduit I is lower, under these circumstances, than that in conduit I9, valve 2| will be forced to its closed position, so that all the air from both superchargers is directed into cabin 20 to supply the demand therefor.

A portion of the heat is removed from the 1 air at low altitudes when the system is operating with valve l3 open, as shown. Assuming that cabin pressure is to be kept at 22 inches of mercury, corresponding to an altitude of 8,000 feet, then for altitudes a certain amount above (depending on the compression ratio of supercharger Hl) 8,000 feet, down to sea level, the pressure in conduit I5 is greater than the pressure in cabin 20, and some air will be admitted through valve 2|. Due to compression, this air will be warmer than atmospheric air and may be too warm for comfort. In this condition of operation, however, supercharger I6 is being driven as a motor and the pressure of air in conduit I9 is less than the pressure in conduit I 5, so that the air in conduit I9 is cooler than the compressed air entering cabin 20 from conduit 2|. Thus, when summer atmospheric temperatures may be too high for comfort, the air expanded in supercharger l6 aids in the cooling of the cabin 20, and under certain conditions, no further cooling of cabin air may be necessary. Fig. 2 shows a system similar in most respects to that shown in Fig. l, but which provides for the cooling and heating of.air under all operating conditions, and like numerals designate like parts described in Fig. 1.

Where the temperature of the atmospheric air varies or is different, by quite an amount, from the temperature which it is desired to maintain in cabin 20, it will be found necessary to cool or to heat the air for the comfort of the passengels. For this purpose a heat exchange unit 24 having an inlet passage 25 and an outlet 26 is positioned about conduit l2 so that heat may be transferred from conduit I2 to heat exchange unit 24 or vice versa, asoperating conditions dictate. A two-position valve 2'! is placed in a Y connection member 28 to which are attached conduits 29 and 30. Valve 21 i manually or motor controlled through a valve arm and connecting rod 3|. As indicated by the legend, cool air, from a source not shown, which may be a ram located in a leading portion of the through heat exchange unit 24 when valve 21 is r in the position shown, and thus additional heat may be imparted to the air under pressure in conduits l2 and I5, so that the air entering cabin 20 may be at a comfortable temperature, even though the atmospheric air is in the zero or minus zero region.

The air delivered to the cabin 20 may be heated or cooled by means of heat transfer device 24. When the superchargers are operating in series, the output conduit l2 being in heat exchange relation to transfer unit 24, the'temperature of the air in output conduit l9 and in cabin 20 can be closely controlled. When the superchargers are operating in parallel, that is, when valve I3 is raised to its closedivertical) position the output of supercharger ID will be diverted through conduit 23 to cabin 20 at the 7 temperature desired, and the input air from scoop I! to supercharger 18 passes through a conduit 32 which, like conduit I2, is in heat exchange relation to heat transfer unit 24, and thus. air in output conduit I 9 may be delivered to cabin 20 at the desired temperature.

An additional valve 33, which may be manually or motor operated through valve arm and rod 34, is placed in conduit 22, and in its closed position, as shown, it prevents the by-passing of any air from supercharger l0 into cabin 20 through conduit 22 at all altitudes, so that when superchargers I0 and I6 are operating in series (twostage), and when it is desired to decrease the air entering cabin 20 to a temperature below that of the external atmosphere, valve 21-is thrown to its right-hand position stoppin the flow of hot air through conduit 30 and permitting cool air to enter heat exchanger 2| through conduit 29, wherein it is circulated about conduit l5, absorbing heat caused by the compression of air in supercharger ID. The temperature of air in input conduit l5, therefore, may be made much lower than the temperature of the external atmosphere. Further, due to the fact that the capacity of supercharger I6 is less than that of supercharger ID, the air in input conduit IE will be at a greater pressure than that in the output conduit I9. Because of its expansion in supercharger l6, the air in conduit l9, and therefore in cabin 20, will be at a lower temperature than that in input conduit ii. The expansion of supercharged air in supercharger l6, increases the amount of cooling that can be obtained by merely passing the supercharged air through the intercooler or heat exchanger 24, and therefore the range of temperature drop between the at-- mospheric air and cabin air is increased beyond the: possible with only a heat exchanger such as In the event that the air expanded by supercharger IB is cooler than desired for cabin 20, the valve 33 may be opened to admit air to cabin 20 from conduits I 5 and 22. This air will pass through check Valve 2! because the pressure of air in input conduit [5 is greater than the pressure in conduit l9 and the temperature of air in conduit IE will be higher than the temperature of air in conduit l9, and the air in conduit 19 will therefore, upon mixing with air in conduit 22, suffer an increase in temperature prior to entrance to cabin 20. If desired valve 33 may be thermostatically controlled in order that it may be opened or closed to maintain the cabin air 20 at its required temperature. 7

While superchargers l and I have been shown as Roots blowers, other types, such as centrifugal superchargers, may be used in the system described.

Valves l3 and 33 may be operated manually by the pilot, or automatically by any conventional pressure responsive device and a relay, but as the particular mode of operating th valves forms no part of the invention, any showing of valve controls has been omitted.

While only two embodiments of the present invention have been shown in the drawing, it is to be understood that various changes may be made without departing from the scope of the present invention. For this reason, it is intended not to limit the invention by the description herein given as an example, but solely by the scope of the appended claims.

What is claimed is:

1. A supercharging system for aircraft cabins including a first supercharger having an air intake and an air exhaust, a by-pass passage connected to said exhaust and to a cabin, a second supercharger of less capacity than said first upercharger, an air intake therefor and a conduit between the input of said second supercharger and the exhaust of said first supercharger, a by-pass valve located at a connection between said conduit and said by-pass passage. an output passage connected to said second supercharger and to said cabin, a check valve in the intake for said second supercharger, a second conduit connected to said conduit between said superchargers and to said cabin, a. check valve therein, and a heat exchanging member arranged in heat transfer relation to the conduit between said superchargers, whereby air compressed in said first supercharger, may sufier a heat exchange with respect to said heat exchanging member and be introduced into said cabin after passage through said second supercharger, at a temperature other than the temperature of air compressed by said first supercharger.

2. A system of cabin supercharging comprising a cabin, an air inlet thereto, a first supercharger of unit capacity having an air inlet and an air outlet, a second supercharger of less than unit capacity having an air intake and an air inlet connected to the air outlet of said first supercharger and an air outlet connected to the air inlet to said cabin, an air by-pass connected to the air inlet to said cabin and to the outlet of said first supercharger, a by-pass valve located in the outlet or said first supercharger at said by-pass connection, control means for the actuation of said valve to selectively place said superchargers in series or in parallel, a communicating channel between the outlet of said first supercharger and the air inlet to said and a check valve therein and opening toward said cabin so that for certain pressure relations when said superchargers are operating in series, a portion of the air compressed by said supercharger may be passed to the inlet of said cabin in parallel with the air passing through said second supercharger.

DAVID GREGG. DONALD M. LAWRENCE.

cabin, 

